[ntp:questions] Inexpensive OEM GPS units?

David Woolley david at ex.djwhome.demon.co.uk.invalid
Wed Nov 14 07:31:44 UTC 2007

In article <13jkondp53g9sa5 at corp.supernews.com>,
cmadams at hiwaay.net (Chris Adams) wrote:

>                   (e.g. how can the offset from "true" be calculated)?

It can't.  If it could, ntpd would compensate for it, with the result
that it would be reduced to a level where it couldn't be calculated.

Normally, finding any systematic offset would require the temporary use
of a time source that was better than your normal time sources.  As I think
you are using USB, which is likely to have a significant impact, you 
would also need to bypass this, either by temporarily feeding the system
with time through a route with lower latency, or by outputting the 
system's idea of the time through a low latency route and comparing it
outside of the system.

The best you can get from the figures is the variability around any
systematic error.

This does assume that the ntpd algorithm is optimal.

Chris Adams <cmadams at hiwaay.net>
Systems and Network Administrator - HiWAAY Internet Services
I don't speak for anybody but myself - that's enough trouble.

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